Shared Stress

Recent studies are indicative of emotions and stress being contagious, but whether it has lasting consequences for the brain is not known. Brain changes associated with stress sustain many mental disorders such as depression, PTSD, and anxiety.

Effects of stress in pairs of mice were examined, removing one mouse from the pair and exposing it to stress before returning it to its partner, then examining responses from specific cells, specifically CRH neuron, in each mouse, that revealed networks in the brains of the stressed mouse and the naive partner were altered in the same way. CRH neurons from the partner which were not directly exposed to actual stress showed changes that were identical to those that were measured in the stressed mouse.

Engineer of these neurons was done using optogenetic approaches so that they could be turned off or on with light. When the neurons were silenced during stress changes in the brain were prevented that typically would occur after stress. When the partner had silenced neurons during interaction with its stressed partner stress stress did not transfer. When light was used to activate the neurons even in the absence of stress both mice brains were changed as they would after being exposed to a real stress.

Activation of CRH neurons causes the release of chemical signals from the mouse that alerts the partner. Partners detecting the signal can in turn alert additional group members. Propagation of stress signals reveals mechanisms for transmission of information that may be important to the formation of social networks in a range of species. Evidence was also found of social networks ability to buffer stress, selectively, by the researchers, noting residual effects of stress on CRH neurons were decreased in females by close to half after spending time with their unstressed partners, but this was not seen in males.

The findings may be present in humans, as we readily communicate stress to others, often without even being aware. Ability to sense another person’s emotional state is a part of building, creating, and maintaining social bonds, there is evidence of some symptoms of stress persisting in loved ones of individuals who suffer from PTSD. Social interactions and stress are linked intricately, consequences of which can be long lasting and may even influence behaviours at a later time.